Autocorrelation central hole estimates in nonlinear photon-counting detectors

In an experiment in which two or more photoevents arriving at the same pixel are considered a single count, a one-pixel-size central hole appears in the autocorrelation estimate. This hole is a source of error when high-resolution techniques based on the autocorrelation function are applied to image or signal recovery. We present an experimental method to evaluate the autocorrelation central hole based on the nonlinear behavior of the total number of counts per frame when clipped photocount distributions are considered. The technique is easy to perform and provides high accuracy.